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Release of Official Maps of Revised Earthquake Fault Zones

December 4, 2015


Five Revised Official Maps of Alquist-Priolo Earthquake Fault Zones were released on December 4, 2015 to Los Angeles, San Bernardino, Orange and Riverside counties, and the cities of Brea, Yorba Linda, Indio and Coachella by the California Geological Survey (CGS).  These maps are released under the authority of the Alquist-Priolo Earthquake Fault Zoning (AP) Act that was passed following the 1971 San Fernando earthquake.  The AP Act is a state law designed to reduce the hazard from surface fault rupture during an earthquake.  Earthquake Fault Zones are regulatory zones that encompass surface traces of active faults that have a potential for future surface fault rupture.


These revised maps show the location of AP Earthquake Fault Zones and Seismic Hazard Zones (if evaluated) and is collectively referred to as Earthquake Zones of Required Investigation.  An electronic version of the zone maps, referred to as a geo-pdf file, can be viewed using Adobe Acrobat Reader.  This geo-pdf file consists of multiple layers and gives the user greater flexibility in viewing and displaying the maps.  Digital Geographic Information System (GIS) files for both AP Earthquake Fault Zones and Seismic Hazard Zones released by CGS are considered the "Official Maps."  Both GIS and geo-pdf files, as well as conventional pdf files, can be downloaded for the December 4 release.  Seismic Hazard Zone GIS files can also be downloaded.


Fault Evaluation Report 7.5 Minute Quadrangles GIS Data
FER 250   Indio
Thermal Canyon
Thermal Canyon
FER 251   Mt. San Antonio
Mescal Creek
Mt. San Antonio
Mescal Creek
FER 258 Yorba Linda  Yorba Linda